Limit Stress Research Articles

Abstract 1307: Community-driven support platform BlueHQ: An innovative solution to address the needs of patients with colorectal cancer

Abstract Background: Colorectal cancer (CRC) is the third-most commonly diagnosed cancer and the second-leading cause of cancer death in men and women combined in the United States. To manage the disease, patients and caregivers turn to various tools and resources for financial assistance, information dissemination, emotional and peer support, and treatment planning, among other critical issues and needs they face. The Colorectal Cancer Alliance (the Alliance) created BlueHQ to provide patients and caregivers with a resource solution encompassing all potential areas of need. Methods: A survey aimed at understanding needs, barriers, and quality improvement opportunities was disseminated via the Alliance's Blue Hope Nation community for two weeks and by email. One hundred sixty-seven colorectal cancer patients and forty caregivers of colorectal cancer patients completed the survey. Results: Patients and caregiver respondents report reliance on external tools and resources to manage disease and support information. Of the support methods, patient respondents reported using social media (46.11%); notebooks, journals, and planners (45.41%); online articles (44.91%); the Blue Hope Nation Facebook group (41.32%); cancer discussion boards (35.33%); and spiritual or religious advice (29.94%). Patients sought financial assistance, local peer support and groups, and mental health help to minimize diagnosis-related stressors. To provide more efficient care and limit stress, the community suggested financial help, communication and support from other patients and caregivers, and informational resources. Conclusions: These survey results are consistent with other published learnings about patient and caregiver reliance on support tools and highlight the myriad resources that patients and caregivers currently use for managing CRC. BlueHQ is a support solution that provides patients and caregivers with access to information and resources tailored to users’ specified profiles, including molecular characteristics of the tumor. Users can also store documents and information from healthcare encounters, creating a longitudinal record and tracking disease progression. In the age of precision oncology, BlueHQ ensures patients and users are presented with personalized educational materials and multimedia resources to help manage their disease and bridge the gaps in patient support. BlueHQ was explicitly designed to connect the CRC community to the latest therapeutic and clinical research resources to improve outcomes and quality of life for all CRC patients. Citation Format: Kimberly Lynn Newcomer. Community-driven support platform BlueHQ: An innovative solution to address the needs of patients with colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1307.

The Oxidative Stress Response Highly Depends on Glucose and Iron Availability in Aspergillus fumigatus.

Pathogens have to cope with oxidative, iron- and carbon(glucose)-limitation stresses in the human body. To understand how combined iron-carbon limitation alters oxidative stress responses, Aspergillus fumigatus was cultured in glucose-peptone or peptone containing media supplemented or not with deferiprone as an iron chelator. Changes in the transcriptome in these cultures were recorded after H2O2 treatment. Responses to oxidative stress were highly dependent on the availability of glucose and iron. Out of the 16 stress responsive antioxidative enzyme genes, only the cat2 catalase-peroxidase gene was upregulated in more than two culturing conditions. The transcriptional responses observed in iron metabolism also varied substantially in these cultures. Only extracellular siderophore production appeared important regardless of culturing conditions in oxidative stress protection, while the enhanced synthesis of Fe-S cluster proteins seemed to be crucial for oxidative stress treated iron-limited and fast growing (glucose rich) cultures. Although pathogens and host cells live together in the same place, their culturing conditions (e.g., iron availability or occurrence of oxidative stress) can be different. Therefore, inhibition of a universally important biochemical process, like Fe-S cluster assembly, may selectively inhibit the pathogen growth in vivo and represent a potential target for antifungal therapy.

Comparison of Eddy Viscosity Models for High Turbulence Nozzle Guide Vane Flows

Abstract In this paper we investigate the performance of eddy viscosity turbulence models for high-pressure nozzle guide vane (NGV) flows with engine-realistic turbulence. Using metrics such as integrated kinetic energy (KE) loss and mixing rate, we compare simulation results using turbulence models with high-fidelity experimental data from fully-cooled NGVs, operating at engine-matched conditions of Reynolds number and Mach. For the widely-used k–ω shear stress transport (SST) model, the aerodynamic and thermal wakes of the NGVs were undermixed. We compare simulation results with those using other common turbulence models including the standard k–ω, baseline k–ω, Spalart–Allmaras, and baseline explicit algebraic Reynolds stress model. Alternative turbulence models formulations are explored, with an emphasis on modifications to the implementation of the shear stress limiter. We also investigate the sensitivity of models to the specified inlet turbulence intensity. We demonstrate that predictions of integrated KE loss, as well as the decay trends of the aerodynamic and thermal wakes are a closer match to experimental data for the baseline algebraic Reynolds stress model than for other turbulence models in more common use for NGV predictions.

Mechanical response and energy evolution of interbedded shales subjected to multilevel constant/increasing-amplitude cyclic loading

This study aims to investigate the effects of fatigue loading paths and interbed structure on the mechanical properties and energy evolution characteristics of shales. In the experiments, shale specimens with five types bedded angles (0°, 30°, 45°, 60°, 90°) were prepared, and multilevel constant-amplitude fatigue loading test (MCFT) and multilevel variable-amplitude fatigue loading test (MVFT) were performed. Results indicated that shale's fatigue behaviors were highly affected by the bedding plane angles and the cyclic loading paths. Specifically, with the increasing of bedding angle, the peak strength, total dissipated energy, and total input energy of the shales showed a "U" trend, the ultimate macro-damage mode changed from mixed tension-shear failure to failure along the bedding planes, and the damping ratio firstly increased and then decreased. Test schemes of stepwise increase of the lower stress limit or keeping it constant were the differences between MCFT and MVFT, which significantly influenced the evolution of irreversible deformation of shales. Compared to MVFT, the shale in MCFT displayed reduction in peak strength in the range of 4.3% to 23.9%, greater and more drastic variations in elastic modulus and damping ratios, dissipative energy and elastic strain energy were relatively low by an order of magnitude.

Stress Analysis of Pin Connections in Steel Box Girder with the Unibridge System using Finite Element Model

This study analyzes the Unibridge system, a modular steel box girder employing two pins for longitudinal connections, thereby expediting construction compared to traditional girders. A finite element model was developed to analyze the stress on these pins in a single-box girder with five segments and a reinforced concrete floor slab. Various loads were applied following the Indonesian bridge loading standard, SNI 1725:2016. The model considers operational load analysis and assumes full composite behaviour between the top flanges of the girder and the concrete floor slab. The results indicate that the Von-Mises stress on the pins reaches a maximum of 490.95 MPa under combined service loads, consistently remaining below the specified material yield stress limit of 1200 MPa. Consequently, the Demand Capacity Ratio (DCR) is 0.41. As a result, the Unibridge girder connection pins do not experience plastic deformation under the applied loads.

A closed-form structural stress-strain relation and implications on plastic design limits in codes and standards

The deformation of elastic-perfectly plastic beam or plate under combined through-thickness membrane and bending stresses (i.e., structural stress) is analyzed in this paper. Closed-form solutions of “plane-remains-plane” strain (i.e., structural strain) distribution as a function of applied stress and yield strength is derived. The relationship between structural stress and structural strain is also revealed for gaining insights on not only the plastic collapse conditions, but also through-thickness deformation behaviors leading to limit state. Based on the closed-form strain solutions, four deformation modes are identified: (1) elastic, (2) one-side yielding, (3) two-side yielding, and (4) plastic collapse. A membrane-bending stress interaction diagram is constructed to depict four zones that are associated with the four deformation modes in the normalized membrane and bending stress space. Closed-form solutions of residual stress, residual strain, and structural stress range-strain range relation after a loading-unloading cycle are also derived. Based on the parabolic plastic collapse stress limit curve, parabolic design stress limit curves with coherent safety margins for any combinations of membrane and bending stresses are constructed. The new insights gained in this study offer a more consistent definition of design stress limit than those used in the current codes and standards, e.g., ASME BP&V Code.

Experimental investigation of probabilistic failure of SiC/SiC composite tubes under multiaxial loading

This paper presents an experimental investigation of the failure behavior of SiC fiber-reinforced SiC matrix (SiC/SiC) composite tubes under multiaxial loading. A new testing apparatus is designed to independently apply axial stress and internal pressure to SiC/SiC tubes. Acoustic emission (AE) is used to monitor the damage growth in the specimen. Based on the measured stress–strain response, a strain-based criterion is proposed to determine the proportional limit stress (PLS). The proposed strain-based criterion is compared with the PLS determined by the AE measurement. The PLS is determined for different loading ratios to form a multiaxial failure surface. By testing multiple replicates, the statistical variations of the PLS are determined. Based on the experimental results, a mathematical model is developed to characterize the probability distribution of the PLS of SiC/SiC composites under multiaxial loading.

Analysis of Wire Breakage Fault Caused by Galloping on 66kV Debao A and B Line in November 2023

In early November 2023, affected by extreme weather conditions such as rain, snow, and freezing, some transmission lines in northeast region experienced icing and galloping, which brought lots of tripping and disconnection faults. Taking the wire breakage faults of the 66kV Debao A and B line as examples, the causes, processes, and characteristics were all detailed analysed. It can be basically identified that after the first-order galloping of icing the wire, due to the lack of or limited effectiveness of anti-galloping measures, interphase flashover occurred. The flashover melted some of the stranded of galloping wire, resulting in dynamic tension caused by galloping concentrated towards the broken position, the remaining cross-section of the stranded. Due to repeated bending and stretching, the remaining stranded wires exceeded the limit of fracture stress, leading to fracture and overall wire breakage and landing. So the wire breakage fault in this case is strongly related to the interphase flashover caused by galloping. This article conducted fault analysis work by collecting line design, on-site meteorological conditions, and fault characteristics, providing technical support for subsequent prevention and control work.

Data-Driven Fatigue Failure Probability Updating of OSD by Bayesian Backward Propagation

This study introduces a data-driven approach for updating the fatigue failure probability of the orthotropic steel deck (OSD) using Bayesian backward propagation. The OSD in steel bridges is considered as a parallel system composed of two critical fatigue-prone components, namely, the rib-to-diaphragm and rib-to-deck joints. A probabilistic model for fatigue reliability is established based on the equivalent structural stress method and limit state function. The system-level fatigue reliability model is then constructed, taking into account the correlations between limit states of individual components through Bayesian network forward propagation. The key advantage of the Bayesian network-based framework is its ability to perform backward propagation, allowing for the updating of failure probabilities for critical components when the system-level failure of the OSD is observed. Consequently, the proposed approach enables the identification of vulnerable components through data-driven fatigue failure probability updating. Finally, the approach is applied to a real instrumented steel bridge to determine the time-dependent fatigue failure probability at both the system and component levels over its service life. The results show that the component-level fatigue failure probability model will underestimate the fatigue life in comparison to the system-level model. Meanwhile, the proposed method could identify vulnerable components by quantifying the fatigue failure probability of in-service steel bridges.

Nutrient limitation and oxidative stress induce the promoter of acetate operon in Salmonella Typhimurium.

Glyoxylate shunt is an important pathway for microorganisms to survive under multiple stresses. One of its enzymes, malate synthase (encoded by aceB gene), has been widely speculated for its contribution to both the pathogenesis and virulence of various microorganisms. We have previously demonstrated that malate synthase (MS) is required for the growth of Salmonella Typhimurium (S. Typhimurium) under carbon starvation and survival under oxidative stress conditions. The aceB gene is encoded by the acetate operon in S. Typhimurium. We attempted to study the activity of acetate promoter under both the starvation and oxidative stress conditions in a heterologous system. The lac promoter of the pUC19 plasmid was substituted with the putative promoter sequence of the acetate operon of S. Typhimurium upstream to the lacZ gene and transformed the vector construct into E. coli NEBα cells. The transformed cells were subjected to the stress conditions mentioned above. We observed a fourfold increase in the β-galactosidase activity in these cells resulting from the upregulation of the lacZ gene in the stationary phase of cell growth (nutrient deprived) as compared to the mid-log phase. Following exposure of stationary phase cells to hypochlorite-induced oxidative stress, we further observed a 1.6-fold increase in β galactosidase activity. These data suggest the induction of promoter activity of the acetate operon under carbon starvation and oxidative stress conditions. Thus, these observations corroborate our previous findings regarding the upregulation of aceB expression under stressful environments.

Experimental study on fatigue failure properties of mudstone interlayers under discontinuous loading in salt cavern gas storage

During the operation of an underground salt cavern gas storage, Fatigue failure occurs in the surrounding rock of gas storage reservoirs under non-continuous gas injection and extraction loading. Due to the special layered salt rock structure in China, the mudstone interlayer is the weak part of the gas storage. It is necessary to study the effect of stress magnitude and interval time on the fatigue mechanical properties of mudstone. Graded upper stress limit interval fatigue (GUIF) test and graded lower stress limit interval fatigue (GLIF) test were carried out on mudstone respectively. And different interval times were set to investigate the effect of interval time on the mechanical properties of mudstone. With the increase in the interval time, the fatigue life and peak strain of the mudstone increased. Under the same interval time, the lower-limit interval test result showed a significantly higher fatigue life than the upper-limit interval test result. The stress–strain curve exhibited three stages: scattered–dense–scattered. During the unloading phase, the modulus of elasticity increased with increasing stress levels, indicating that the internal structure of the mudstone is extremely sensitive to the stress. In the (GUIF) test, the average residual strain increased with the increase in the interval time, and the residual strain during the cycle after the time interval under different grades was lower than the residual strain before the time interval; the results of the (GLIF) test showed the opposite trend. In the (GUIF) test, the average creep strain increased with increasing interval time under the same stress level, and the average creep strain was greater than the average residual strain, and the creep stage had a greater effect on mudstone damage than the fatigue stage. The post-fatigue creep strain was significantly greater than the pre-fatigue creep strain. The research results can be useful in ensuring the stable operation of gas storage in salt caverns.

Does the Larkin length exist?

The yield stress of random solid solutions is a classic theme in physical metallurgy that currently attracts a renewed interest in connection to high entropy alloys. Here, we revisit this subject using a minimal dislocation dynamics model, where a dislocation is represented as an elastic line with a constant line tension embedded in the stochastic stress field of the solutes. Our exploration of size effects reveals that the so-called Larkin length (Lc ) is not a length scale over which a dislocation can be geometrically decomposed. Instead, Lc is a crossover length scale marking a transition in dislocation behavior identifiable in at least three properties: (1) below Lc , the dislocation is close to straight, aligned in a single energy valley, while above Lc , it roughens and traverses several valleys; (2) the yield stress exhibits pronounced size-dependence below Lc but becomes size-independent above Lc ; (3) the power-spectral density of the dislocation shape changes scaling at a critical wavelength directly proportional to Lc . We show that for white and correlated stress noises, Lc and the thermodynamic limit of the yield stress can be predicted using Larkin’s model, where the noise dependence in the glide direction is neglected. Moreover, we show that our analysis is relevant beyond the minimal line tension model by comparison with atomic-scale simulations. Finally, our work suggests a practical approach for predicting yield stresses in atomistic models of random solid solutions, which only involves small-scale atomistic simulations below Lc .

Characterizing the flavodoxin landscape in Clostridioides difficile.

The gram-positive, anaerobic, and spore-forming bacterium Clostridioides difficile has become a vast problem in human health care facilities. The antibiotic-associated infection with this intestinal pathogen causes serious and recurrent inflammation of the intestinal epithelium, in many cases with a severe course. To come up with novel targeted therapies against C. difficile infections, a more detailed knowledge on the pathogen's physiology is mandatory. Eight putative flavodoxins, an extraordinarily high copy number of this type of small electron transfer proteins, are annotated for C. difficile. Flavodoxins are known to be essential electron carriers in other bacteria, for instance, during infection-relevant conditions such as iron limitation and oxidative stress. This work is a first and comprehensive overview on characteristics and expression profiles of the putative flavodoxins in the pathogen C. difficile.

Phenotypic and transcriptional characterization of F. tularensis LVS during transition into a viable but non-culturable state.

Francisella tularensis is a gram-negative, intracellular pathogen which can cause serious, potentially fatal, illness in humans. Species of F. tularensis are found across the Northern Hemisphere and can infect a broad range of host species, including humans. Factors affecting the persistence of F. tularensis in the environment and its epidemiology are not well understood, however, the ability of F. tularensis to enter a viable but non-culturable state (VBNC) may be important. A broad range of bacteria, including many pathogens, have been observed to enter the VBNC state in response to stressful environmental conditions, such as nutrient limitation, osmotic or oxidative stress or low temperature. To investigate the transition into the VBNC state for F. tularensis, we analyzed the attenuated live vaccine strain, F. tularensis LVS grown under standard laboratory conditions. We found that F. tularensis LVS rapidly and spontaneously enters a VBNC state in broth culture at 37°C and that this transition coincides with morphological differentiation of the cells. The VBNC bacteria retained an ability to interact with both murine macrophages and human erythrocytes in in vitro assays and were insensitive to treatment with gentamicin. Finally, we present the first transcriptomic analysis of VBNC F. tularensis, which revealed clear differences in gene expression, and we identify sets of differentially regulated genes which are specific to the VBNC state. Identification of these VBNC specific genes will pave the way for future research aimed at dissecting the molecular mechanisms driving entry into the VBNC state.

Integration analysis of ATAC-seq and RNA-seq provides insight into fatty acid biosynthesis in Schizochytrium limacinum under nitrogen limitation stress

BackgroundSchizochytrium limacinum holds significant value utilized in the industrial-scale synthesis of natural DHA. Nitrogen-limited treatment can effectively increase the content of fatty acids and DHA, but there is currently no research on chromatin accessibility during the process of transcript regulation. The objective of this research was to delve into the workings of fatty acid production in S. limacinum by examining the accessibility of promoters and profiling gene expressions.ResultsResults showed that differentially accessible chromatin regions (DARs)-associated genes were enriched in fatty acid metabolism, signal transduction mechanisms, and energy production. By identifying and annotating DARs-associated motifs, the study obtained 54 target transcription factor classes, including BPC, RAMOSA1, SPI1, MYC, and MYB families. Transcriptomics results revealed that several differentially expressed genes (DEGs), including SlFAD2, SlALDH, SlCAS1, SlNSDHL, and SlDGKI, are directly related to the biosynthesis of fatty acids, meanwhile, SlRPS6KA, SlCAMK1, SlMYB3R1, and SlMYB3R5 serve as transcription factors that could potentially influence the regulation of fatty acid production. In the integration analysis of DARs and ATAC-seq, 13 genes were identified, which were shared by both DEGs and DARs-associated genes, including SlCAKM, SlRP2, SlSHOC2, SlTN, SlSGK2, SlHMP, SlOGT, SlclpB, and SlDNAAF3.ConclusionsSlCAKM may act as a negative regulator of fatty acid and DHA synthesis, while SlSGK2 may act as a positive regulator, which requires further study in the future. These insights enhance our comprehension of the processes underlying fatty acid and DHA production in S. limacinum. They also supply a foundational theoretical framework and practical assistance for the development of strains rich in fatty acids and DHA.

Accurate Finite Element Simulations of Dynamic Behaviour: Constitutive Models and Analysis with Deep Learning.

Owing to the challenge of capturing the dynamic behaviour of metal experimentally, high-precision numerical simulations have become essential for analysing dynamic characteristics. In this study, calculation accuracy was improved by analysing the impact of constitutive models using the finite element (FE) model, and the deep learning (DL) model was employed for result analysis. The results showed that FE simulations with these models effectively capture the elastic-plastic response, and the ZA model exhibits the highest accuracy, with a 26.0% accuracy improvement compared with other models at 502 m/s for Hugoniot elastic limit (HEL) stress. The different constitutive models offer diverse descriptions of stress during the elastic-plastic response because of temperature effects. Concurrently, the parameters related to the yield strength at quasi-static influence the propagation speed of elastic waves. Calculation show that the yield strength at quasi-static of 6061 Al adheres to y = ax + b for HEL stress. The R-squared (R2) and mean absolute error (MAE) values of the DL model for HEL stress predictions are 0.998 and 0.0062, respectively. This research provides a reference for selecting constitutive models for simulation under the same conditions.

Comparative Study on Complete Characterisation of Elastic–Ductile Compressive Behaviour of Aged and New Norway Spruce Timber

ABSTRACT Material properties of historical timber structures may change over time due to decay, change of chemical composition of material, biological agents, climatic conditions, etc. Adequate bending performance requires stiffness and strength both in tension and compression, as well as sufficient ductility in compression. While the focus of most research is on the former quantities, the latter one is generally disregarded. This study gives a comparative analysis on complete characterization of compressive behaviour of recent and 60-years-old aged spruce timber (Picea abies). Parallel-to-grain compressive tests on small-sized specimens were conducted to obtain stress – strain diagrams and to determine failure modes. All material properties of stiffness, strength, and ductility were calculated for each specimen. It was concluded that elastic stiffness, elastic limit stress, and compression strength are virtually invariable after sixty years of service while the ductility decreased and the post-peak behaviour became more brittle. It is also found that end-rolling failure mode can yield the same elastic and stiffness properties as the standard kinkband failure. Climatic changes increase the risk of material deterioration prompting for more thorough monitoring and study of historical timber structures.

Prediction of fatigue limit stress in C/SiC composites: Effect of stochastic load spectrum

AbstractUnder cyclic‐fatigue loading, stochastic loading may occur and affect the fatigue limit stress (FLS) in C/SiC composites. In this paper, the FLSs in different C/SiC composites were predicted considering stochastic loading spectrums. Damage mechanisms of interface wear and fibers failure were considered in the global load sharing criterion to determine the fracture life and fiber's failure probability in three different stochastic loading spectrums, that is, constant, increasing and decreasing stochastic stress spectrum. Experimental FLS and fatigue life degradation rate were predicted using the developed micromechanical approach, and the effect of cyclic duration under stochastic spectrums on the FLS was analyzed. Relationships among the FLS, life degradation rate, stochastic spectrum, and cyclic duration were established.

Land management shapes drought responses of dominant soil microbial taxa across grasslands.

Soil microbial communities are dominated by a relatively small number of taxa that may play outsized roles in ecosystem functioning, yet little is known about their capacities to resist and recover from climate extremes such as drought, or how environmental context mediates those responses. Here, we imposed an in situ experimental drought across 30 diverse UK grassland sites with contrasting management intensities and found that: (1) the majority of dominant bacterial (85%) and fungal (89%) taxa exhibit resistant or opportunistic drought strategies, possibly contributing to their ubiquity and dominance across sites; and (2) intensive grassland management decreases the proportion of drought-sensitive and non-resilient dominant bacteria-likely via alleviation of nutrient limitation and pH-related stress under fertilisation and liming-but has the opposite impact on dominant fungi. Our results suggest a potential mechanism by which intensive management promotes bacteria over fungi under drought with implications for soil functioning.

Evaluation of Different Subperiosteal Implant Thicknesses on Mechanical Strength and Stress on Bone by Finite Element Analysis.

Implants have always been within the interest of both clinicians and material scientists due to their places in reconstructive and prosthetics surgery. Excessive bone loss or resorption in some patients makes it difficult to design and manufacture the implants that bear the necessary loads to carry the final prosthetics. With this study; we tried to determine the minimum material thickness of the subperiosteal implants that can withstand the physiological forces. We have created a digital average bone structure based on actual patient data and designed different subperiosteal implants with 1, 1.5, and 2mm material thicknesses (M1, M2, M3) for this digital model. The designed implant models are subjected to 250 Newtons (N) of force, and the implant and bone are tested for the stress they are exposed to, the pressure they transmit to, and their mechanical strength with Finite Element Analysis with the physical parameters boot for the implant material and human bone. Results show us that under specific design parameters and thicknesses, the 1mm thickness design failed due to exceeding the yield stress limit of 415MPa with a 495,44MPa value. The thinnest implant showed plastic deformation and transmitted excessive forces, which may cause bone resorption due to residual stress. We determined that thinner subperiosteal implants down to 1.5mm that have the necessary material parameters for function and tissue support can be designed and manufactured with current technologies.